Weeds cost farmers billions of dollars annually in crop losses and in the expense of keeping weeds under control. Much of the cost of intertillage of row crops, maintenance of fallow, seedbed preparation, and seed cleaning is chargeable to weed control. Suppression of weeds along highways and railroad right-of-ways, and in irrigation ditches, navigation channels, yards, parks, grounds, and home gardens also is expensive. Ragweed pollen is the source of annual periodic distress to several million hayfever sufferers. Poison ivy, poison oak, poison sumac, nettles, thistles, sandburs, and puncturevine also bring pain to millions. Weeds also serve as hosts for other crop diseases as well as for insect pests.
The losses caused by weeds in agricultural production environments include decrease in crop yield, reduced crop quality, increased irrigation costs, increased harvesting costs, decreased land value, injury to livestock, and crop damage from insects and diseases harbored by the weeds.
Chemical herbicides have provided an effective method of weed control; however, the public has become concerned about the amount of residual chemicals which might be found in food, ground water, and the environment. Stringent new restrictions on the use of herbicides and the elimination of some effective herbicides from the market place could limit economical and effective options for controlling costly weeds. Additionally, the visually apparent phytotoxic effects of some systemic herbicides appear very slowly on the target weeds, so pesticide users often seek methods by which the apparent speed of action of the herbicide is increased.
There is a great need for novel weed control methods which reduce the amount of chemical herbicide necessary to obtain acceptable levels of weed control. Researchers have experimented with various combinations of chemicals as one approach to identify compositions which have desirable herbicidal characteristics. In the rare instance, unexpected activity of the combination of chemicals is obtained. For example, selective control of annual weeds with a composition of fatty acids mixed with ethylmaleimide, colchicine, 2,4-dinitrohalobenzene, or 2,4-dinitrophenol has been described in the Japanese patent abstract JP61106501. It should be noted that the compounds which were mixed with the fatty acids are not known for their agricultural use and, in fact, may be inappropriate for many herbicidal applications. Other abstracts disclosing a variety of fatty acid derivatives with various chemical compounds include JP59199608 (halogen or cyano derivatives of fatty acids with 2-amino 1,2,4-triazole), JP59199609 (halogen or cyano derivative of fatty acid with 3-amino 1,2,4-triazole), and JP59193804 (acetylenic derivative). Unlike the abstracts mentioned above, the current invention pertains to certain combinations of fatty acids and chemical herbicides which can provide broad range or selective herbicidal activity.